I'm sorry, you will have to do the historical research needed to answer questions about the state of the software in the distant past.
The limit at one time was 256. It was raised some time ago to 1024 - probably waste of effort, since applications that generate more than 256 prefixes for the same namespace are probably going to generate more than 1024 eventually. I'm afraid that applications that do this (or rather, the documents that they generate) cannot be processed by Saxon; you will have to do some preprocessing to get rid of the redundant prefixes, or change the application that generates the document to adopt a more sensible strategy.
Michael Kay

From: Fernando Ribeiro [mailto:webmaster@fernandoribeiro.eti.br]
Sent: 20 October 2008 04:31
To: Mailing list for the SAXON XSLT and XQuery processor
Subject: [saxon] Maximum Prefixes per URI in Saxon 8.4


How many prefixes can be mapped to the same URI in Saxon 8.4?